Aluminum oxide supported gas permeable membranes

Abstract

A semi-porous composite membrane and a method of manufacturing the semi-porous composite membrane. The semi-porous composite membrane includes a base supporting substrate comprising α-Al 2 O 3 , an outer layer comprising silica, and an intermediate layer comprising crystalline fibers of boehmite, and at least one of a secondary metal oxide and a synthetic polymer, wherein the intermediate layer is disposed between the base supporting substrate and the outer layer. The crystalline fibers of boehmite are a length of 5-150 nm. The semi-porous composite membrane may be employed in membrane reactors.

The invention claimed is: 
     
       1. A semi-porous composite membrane comprising:
 a base supporting substrate comprising α-Al 2 O 3 ; 
 an outer layer comprising silica; and 
 an intermediate layer comprising crystalline fibers of γ-Al 2 O 3  which are a length of 5-150 nm and at least one of a secondary metal oxide and a synthetic polymer, wherein the intermediate layer is disposed between the base supporting substrate and the outer layer; 
 wherein the semi-porous composite membrane has a permeance of 4.0×10 −8  mol·m −2 ·s −1 ·Pa −1  to 1.0×10 −6  mol·m −2 ·s −1 ·Pa −1  for He and H 2  from at least one gas of Ar, N 2 , and CO. 
 
     
     
       2. The semi-porous composite membrane of  claim 1 , wherein the secondary metal oxide is at least one metal oxide selected from the group consisting of lanthanum oxide, zirconium dioxide, calcium oxide, and gallium oxide. 
     
     
       3. The semi-porous composite membrane of  claim 1 , wherein the base supporting substrate is a tubular-shaped support. 
     
     
       4. The semi-porous composite membrane of  claim 3 , wherein the tubular-shaped support has a length of 1 cm to 10 cm, an outer diameter of 0.1 cm to 1 cm, and an inner diameter of 0.05 cm to 0.9 cm. 
     
     
       5. The semi-porous composite membrane of  claim 1 , wherein the base supporting substrate is a porous base supporting substrate. 
     
     
       6. The semi-porous composite membrane of  claim 5 , wherein the porous base supporting substrate comprises pores having an average diameter of 50 nm to 160 nm. 
     
     
       7. The semi-porous composite membrane of  claim 1 , wherein the intermediate layer comprises pores of which 70% -95% of a total number of the pores have a pore size distribution from 2 nm to 70 nm. 
     
     
       8. The semi-porous composite membrane of  claim 1 , wherein the outer layer is a silica membrane. 
     
     
       9. The semi-porous composite membrane of  claim 8 , wherein the silica membrane is a porous silica membrane comprising pores having an average pore diameter of 0.1 nm to 2 nm. 
     
     
       10. The semi-porous composite membrane of  claim 1 , wherein the synthetic polymer is present and is at least one polymer selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, poly(N-(2-hydroxyropyl) methacrylamide, and polyoxazoline. 
     
     
       11. A method of manufacturing a semi-porous composite membrane comprising:
 contacting a base supporting substrate comprising α-Al 2 O 3  with an intermediate layer coating mixture comprising a boehmite sol gel, and at least one if a secondary metal oxide-forming compound and 1-10 wt % of a synthetic polymer relative to a weight of the intermediate layer coating mixture to form a coated substrate; 
 calcining the coated substrate in air at a temperature of 500° C. to 700° C. for 45 minutes-2 hours, with a rate of heating and a rate of cooling of 0.5° C./min-3° C./min; 
 contacting the coated substrate with a silica sol gel mixture comprising a hydrolyzed and condensed silicate ester and an, alcohol and wherein the silica sol gel mixture has a pH of 1 to 3, to form a silica coated substrate; 
 calcining the silica coated substrate in air at a temperature of 500° C. to 700° C. for 45 minutes-2 hours, with a rate of heating and a rate of cooling of 0.5° C./min-3° C./min, which forms an outer layer; and 
 treating the silica coated substrate with a hydrothermal process under a nitrogen gas to steam mixture to form the semi-porous composite membrane; 
 wherein the semi-porous composite membrane has a permeance of 4.0×10 −8  mol·m −2 ·s −1 ·Pa −1  to 1.0×10 −6  mol·m −2 ·s −1 ·Pa −1  for He and H 2  from at least one gas of Ar, N 2 , and CO, at a temperature range of 100° C.-600° C. 
 
     
     
       12. The method of  claim 11 , further comprising repeating the contacting of the coated substrate with the intermediate layer coating mixture and calcining of the coated substrate. 
     
     
       13. The method of  claim 11 , further comprising repeating the contacting of the silica coated substrate with the silica sol gel mixture and the calcining of the silica coated substrate. 
     
     
       14. The method of  claim 11 , wherein the synthetic polymer is at least one polymer selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, poly(N-(2-hydroxypropyl) methacrylamide), and polyoxazoline. 
     
     
       15. The method of  claim 11 , wherein a ratio of nitrogen gas to steam in the nitrogen gas to steam mixture is 1:2 to 1:4 and the hydrothermal process is conducted at a temperature of 350° C. -650° C. 
     
     
       16. The method of  claim 11 , wherein the hydrothermal process may be a pulsed process or a continuous process. 
     
     
       17. The method of  claim 11 , further comprising pre-heating the silica coated substrate to a temperature of 500° C. to 700° C. for 0.5 hour to 1.5 hours immediately before treating the silica coated substrate with the hydrothermal process. 
     
     
       18. The method of  claim 11 , wherein the secondary metal oxide-forming compound is present in the intermediate layer coating mixture and is at least one selected from the group consisting of lanthanum nitrate, zirconium nitrate, calcium nitrate, and gallium nitrate, or hydrates of said lanthanum nitrate, zirconium nitrate, calcium nitrate, and/or gallium nitrate.